Multimeter use for testing cable thicknees & ampage

[alovella]

Hi all, I have a multi meter & wish to know how I use this to test the correct thickness of the cable used say for a shower as I've got a friend who has moved into a flat where he has been having a few issues with the shower. It's believed the last owner may have installed the incorrect cable for the shower but as he has done a good job of burying this cable, there is no way I can tell without doing a test as to what cable size he has used. I Know the Shower should be running off a 32amp fuse but again the last owner has failed to pen in the name SHOWER as there is more than one 32A fuse. Thanks in advance

 

[breezer]

a multi meter will be of no use to you what so ever in this instance.

I suggest you get some one in to look at it for you, or post the problem with the shower.

I am sorry to say bit your obvious lack of understanding is some what concerning

(This is not to be taken personally since i do not know you, it is however based on what you have so far typed)

 

[alovella]

Well, I used to be an electrician about 18yrs ago but was hit by a car, knocked 14ft in the air & 50ft down road. Smashed many bones. No shoulder joint left in right side & left shoulder smashed beyond repair. Lost right arm. but worst thing was head injuries. Everything I learned as an electrian had been wiped clean from my memory so I'm having to try to learn the basics all over again. Very frustrating but I love electrical work & the challenge but since my accident many new rules & regs have come into play so as much as I'm getting bits of my memory with regards to elecs back, it's a challenge, what with all the new things that have come out and changed. As far as wiring a whole house from scratch, I've no problem with this apart from my mobility through disablement but it's getting used to using test meters again that I'm finding hard getting back into. Put it this way. Everything I need to know has to be kept on paper so I can keep track because of my head injury. Many thanks

 

[Aardvark Avo]

If your deciding to install a shower then from jan 2005 needs either a building notice prior to commencing to your LABC.
Or it must be installed by a part "p" qualified electrician.

Failure to follow this you will risk refusal of any insurance claim if you have a problem and upto £5000 fine.

upto 7.2kw 6mm
over 7.2kw 10mm

taken from electricians guide to building control(IEE green book)

 

[breezer]

alovella, sorry to hear that

 

[Space cat]

there is no way I can tell without doing a test as to what cable size he has used

Surely you can see the cores where they go into the CU, the switch or the shower itself. To do it with a meter you would first need to know the length of the cable. Next you would have to get access to the ends of the cores to short live and neutral at one end and measure the resistance between them at the other end. But if you could do that you would be looking at the cores ---

I Know the Shower should be running off a 32amp fuse but again the last owner has failed to pen in the name SHOWER as there is more than one 32A fuse

Fuses for ring mains will have at least two wires coming out of them. Pull out any with single wires (start with the thickest) and see what doesn't work.

 

[festa]

For testing cable gauge then a micrometer is what you need.
You can buy these from places like MAPLIN or the like, i did and only use it for instances you describe when you cant be 100% sure what size cable your dealing with, although with a few years experience you`ll know a size just by first glance but its better safe than sorry.
As mentioned above cable size and protection for the cable can only be advised when the power of the shower and the installation method is known.

Method 1 (clipped direct)(kept away from insulation)
8kw......40A...6mm T&E
8.5kw...40A...6mm T&E
9kw......40A...6mm T&E
9.5kw...45A...6mm T&E (but its close to its limit so personally..10mm)
10kw....45A...10mm T&E
10.5kw.50A...10mm T&E

 

[JohnD]

For testing cable gauge then a micrometer is what you need.

a very easy and cheap way is to carry a few cable clips in your pocket (with the pin removed!) you can mark them with a permanent pen.

Handy for sizes like 4mm which you may not handle often enough to be sure.

 

[briwire]

You need a micrometer or a vernier to measure the diameter of a strand in the cable. I don't know off hand what the various cable strands sizes are, but I'm sure someone on here will know them. For example 7/1.05 might be 6mm.

If you don't know them, just divide the diameter of a strand by 2 for the radius. Square it. Then multiply by Pi (3.142). This gives the cross sectional area of the stramd. Then multiply by the number of strands to give the overall cross sectional area of the cable-dead easy. You probably won't be bang on but close enough to determine whether it is 4mm or 6mm, 16 or 25 etc.

 

[JohnD]

 

[bengasman]

how do you know the reduction factor that should be applied if you can not see the whole lenght of the cable? you might have the right cable for the shower but if it goes through insulation, you will need a bigger cable.

 

[festa]

unfortunately a good search is needed to follow the cable from shower to C.U but if you cant be sure then use the worse case scenario ...
All relevant installation methods can be found in various publications (IEE on site guide or BS7671 16TH edition)